California Medical Assn. officials announced Thursday that they had sued Blue Shield of California alleging that the health insurer's new online doctor rating system is inaccurate and misleads consumers.

Blue Shield's Blue Ribbon Recognition Program, launched in June, analyzed about 6,000 doctors statewide and posted blue ribbons on its website next to the names of those who met national standards for quality care.

The medical association, which represents about 35,000 doctors statewide, alleges that the ratings fail to take into account information from patient medical charts, patient outcomes and previous treatment, in part because the program relies only on a few years of claims data from five insurance products sold by three large health plans (Blue Shield of California, Anthem Blue Cross and UnitedHealthCare).

The suit, filed in Alameda County Superior Court, also alleges Blue Shield failed to give doctors an opportunity to correct errors in the ratings, which the association says steered patients to cheaper physicians.

"By using and publicizing what is a faulty assessment of physicians, without adequate disclosures of the limitations and faults in the ratings, Blue Shield is both misleading the public and potentially damaging the reputations of thousands of doctors," said Dr. Brennan Cassidy, the association's president. "The art and science of medicine is complicated, and any ratings system should reflect that complexity. This is not restaurant service."

The lawsuit demands an injunction and damages. Lead plaintiffs include Dr. Richard Stern, a San Pablo cardiologist.

"This is a flawed process that requires hours of physician time to correct extremely inaccurate data," Stern said in a Thursday statement. "I found that my ratings report was inaccurate after spending significant time reviewing the report against my patient records."

Blue Shield officials defended the ratings Thursday, noting their website includes a disclaimer qualifying the ratings as only one measure of physician quality.

"We understand that it can be very uncomfortable to be rated and ranked," said Dr. Michael-Anne Browne, Blue Shield's Medical Director for Quality, based in Los Angeles, adding, "We stand by our methodology."

Browne rejected the allegation that Blue Shield used the ratings to guide patients to lower-cost doctors.

"There was absolutely no cost data used in this process at all," she said.